Presentation on theme: "Brazilian Tunable Filter Imager (BTFI) Preliminary Design Review (PDR) USP-IAG Universidade de São Paulo 18-19th June 2008 iBTF module Prototyping Version."— Presentation transcript:
Brazilian Tunable Filter Imager (BTFI) Preliminary Design Review (PDR) USP-IAG Universidade de São Paulo 18-19th June 2008 iBTF module Prototyping Version 1.0
Fundamentals In order to effect dispersion cancellation at all angles of the VPH grating (VPHG) pair (between 25° and 45°): 1. The grating rulings of the VPHGs are required to be parallel; ~1’ or ~30 m at edge 2.The surfaces of the VHG gratings (VPHGs) are required to be parallel; R X ~3” ; T X ~1’ – constrained not by counter-dispersion requirement but to avoid image motion with scan Furthermore, in order to scan the iBTF in wavelength: 3.The image transmitted by the VPHG pair should remain stationary during the wavelength scan; 1-pixel ~10” – but more relaxed with flexure monitoring
Coordination Motor identification: M1 – Fixed rotation stage M2 – Moving rotation stage M3 – Linear translation stage on which M2 is moved Fundamental axes of the iBTF P : Z-axis: defined by the linear translation stage on which M2 is mounted X-axis: defined by the rotation axis of M1 Y-axis: experimentally defined by the gravitational vector in the plane of rotation of M1
iBTF P geometry Input optical axis (O-axis) Translation stage (Z-axis – M3) – O&Z-axes should be coincident Rotation axis of M1 (X-axis) – X-axis & O/Z-axis should be orthorgonal – Rotation axis of M2 should be parallel to M1 Y-axis defined by gravity vector (arbitrary) Grating surfaces (VPHG 1 & 2 ) should be coincident with X-axes of M1&M2 Grating rulings of VPHG 1 & 2 should be parallel – Requires rotation @ y-axis … to what tolerance?
Alignment Procedure Mounting of iBTF P and laser on optical bench – Laser directed along z-axis; y-axis defined by gravity vector Zero-point and rotation direction of M1 and M2 – Defined using software control of M1 and M2 Establishing Y-axis alignment with the gravitational vector – Accurate spirit level Establishing parallelism between rotation axes of M1 and M2 – Rotation @ y-axis unavailable; require shims on motor mount Establishing laser alignment with the Z-axis – Use pin-hole and z-translation stage (M3) Establishing orthogonality of M2 mirror surface with Z-axis – No rotation @ y-axis – used mirror on 2D mount Establishing orthogonality of M1 mirror surface with Z-axis – Again no y-axis adjustment on M1 Establishing orthogonality of the Z-axis with the X-Y plane – Uncritical (tbd)
Still to be done Final alignment using: – Laser, 2D-adjustable mirrors, shims and spirit-level Install VPHGs – from Ondax (Rx ; doped-glass) Check dispersion cancellation Check stationarity of image during scan
Preliminary conclusions Basic z-configuration design works? – Electro-mechanically – Yes – Optically Reflection tests – Yes Dispersion tests – Probably (tbc) What needs to be changed? – Y-axis adjustment of M2 Shims will be adequate – Y-axis adjustment of grating mount Design modification in hand Fundamental conclusion – iBTF P = iBTF module in BTFI